UV HARD-CATINGS DEVELPMENTS WITH CATINIC LIGMERS J.M.Francès, S.Schneider, V.Hantin, G.Pibre* PolyRay March 18 th, 2009
Introduction General Hard-Coatings verview Thermal process UV process UV Cationic ligomers in Bluestar Silicones Film properties Thanks to silicones Weather Resistance Description Application example 2
General Hard-Coating verview Why Developing Hard-Coatings? Cost benefits Energy saving Weight decrease Design flexibility Ex.: Replace glasses by transparent plastics in transports Plastics need protection Hard-Coatings What are Hard-Coatings? Thin film (5-15µm) Transparency Surface friction control Material Glass Poly(methyl methacrylate) Polycarbonate Poly(ethylene terephthalate) Scratch resistance UV protection Density (g.cm -3 ) 2,5 1,2 1,2 1,41 3
General Hard-Coating verview Thermal Process Hydrolysis Silanol condensation 4
General Hard-Coating verview Thermal Process Process in the case of a primerless Hard-Coat Substrate cleaning Hard-Coat storage Filter Hard-Coat application Hard-Coat Flash-off 20-30 C 5-20min Thermal curing 130 ± 2 C 20-30min Control measurements 5
General Hard-Coating verview Cationic UV Process Initiation Propagation Difunctionnal oligomers Network 6
General Hard-Coating verview Thermal Process vs UV Process Thermal UV cure Inorganic based upon silicon chemistry Highest industry performance Long term protection Thickness = 5-7µm Simulate a glass surface Solvent rganic based upon silicon modified oligomers Reduced process time Middle term protection Thickness = 5-15µm Improved abrasion resistance over conventional paints May be solvent less Thermal respect of the support 7 Plastic Poly(methyl methacrylate) Polycarbonate Poly(ethylene terephthalate) Tg ( C) ~80-110 ~150 ~110
UV Cationic ligomers in Bluestar Film Properties Cationic vs Free Radical Polymerization Lower shrinkage Improved adhesion No 2 inhibition Shrinkage (%) Filler Content (%) 8
UV Cationic ligomers in Bluestar Photoinitiator Rhodorsil PI2074 Excellent compatibility with UV epoxy polymers High solubility with silicones, hydrophobic Good activation with sensitizers High reactivity Excellent cure response to UV-C radiation ligomers Silicone Si Si Si n rganic : 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane Nano-Fillers Q resins: colloidal silica (~20nm) T resins: silsesquioxane (~1.5nm) 9
UV Cationic ligomers in Bluestar Hard-Coatings Properties Adhesion on support (ASTM-D3359: cross-hatch test) Abrasion resistance (Taber: rotating wheels, ASTM-D4060) Hardness (ASTM-D3363, pencil) Light resistance (QUV - UVB313) 10
UV Cationic ligomers in Bluestar Photoinitiator Amount Effect 8 7 Film Performance (u.a) 6 5 4 3 2 1 0 0 1 2 3 4 5 PhotoInitiator content (u.a.) Post-cure No Post-cure ptimum amount Temperature effect Too much = film destruction / absorption of the light by PI 11
UV Cationic ligomers in Bluestar Thanks to Silicones UV stability Chemical resistance Clarity Thermal stability Good flow characteristics Stain resistance Silicone oligomer amount 12
UV Cationic ligomers in Bluestar Protection of the Substrate 320 280 100 UV solar spectrum measured on the ground UV solar irradiance: 8.3% (filtered by ozone layer: 6.5%) Polymer degradation: free radicals (chain scission, impurities) reaction with polymer chain and 2 Yellowing, loss of gloss, cracks 13
UV Cationic ligomers in Bluestar Protection of the Substrate: Quenchers Anti-free radicals: - Hindered phenols - Hindered Amine Light Scavenger migration, leaching, colored compounds 14
UV Cationic ligomers in Bluestar Protection of the Substrate: organic UV absorbers Chemical absorbers: - Cinnamate, - salicylate, dibenzoylmethane - Stabilization of the excited state Low band gap (use of different molecules) Photodegradation 15
UV Cationic ligomers in Bluestar Protection of the Substrate: organic UV absorbers R H Me N N Me N Me Me 0,5 Triazine like R2 Absorbance (ua) 0 280 300 320 340 360 380 400 420 λ (nm) R1 R3 Benzophenone like R1 N N N R3 R2 Benzotriazole like R1 H R3 N N R2 R4 H xanalide like 16
UV Cationic ligomers in Bluestar Protection of the substrate: Physical blockers - Inorganic - Absorption & diffusion of UV light - First generation: Ti 2, Zn = white pigments (particles ~80-100nm) - high absorption in UV + straight edge of absorption high refractive index in visible light High stability Photocatalysis effect (ex. Ti 2 Si 2 surface layer) 17
UV Cationic ligomers in Bluestar Inorganic Protection of the Substrate Product profile - UV absorption - 3.1eV (400nm) - broad peak (UVA+UVB) - intense peak (few material) - Transparence in visible light: - No absorption lower than 3.1eV - Low refractive index - chemical / regular constraints 18
UV Cationic ligomers in Bluestar Protection of the Substrate: Ce 2 a nice candidate Refractive index = 2,2 Low gap = 3,25eV Anion-cation charge transfert 100 90 80 Transmission (%) 70 60 50 40 30 20 10 0 200 250 300 350 400 450 500 550 600 650 700 Wavelength (nm) UV-Visible transmission of a nano cerium sol (1g.L -1 ) 19
UV Cationic ligomers in Bluestar Protection of the Substrate: rganic vs Inorganic Substrate = PC 50 45 Micro-cracks 40 35 30 YI 25 20 15 10 5 0 0 500 1000 1500 2000 2500 3000 3500 4000 Time (h) PC HC sans add 0.5% rga1 1% rga1 1.3% NanoCe2 20
UV Cationic ligomers in Bluestar UV protection of the substrate: Nano Ce 2 Substrate = PC 12 Cover Slip Hard-Coat Hard-Coat + Nano Ce 2 10 8 delta E 6 4 2 0 0 10 20 30 40 50 60 70 Time (days) PC 0% Ce2 1,4% 2,1% 3,8% 5,1% 21
Conclusion UV Hard-Coatings Advantages vs thermal process Weather protection rganic: efficiency, life time Inorganic: compatibility, dispersion Silicone oligomers Tune surface properties Enhance weather resistance What Next Complete study with the cure speed, Thermal study of the film 22
Further Information Questions are welcome http://www.bluestarsilicones.com 23